The present invention generally relates to a planar circuit housing for a microwave band planar circuit or a millimeter-wave band planar circuit, and more specially relates to a such a planar circuit housing in which an upper cavity and a lower cavity have the same sizes in direction parallel with the planar circuit substrate.
FIG. 1 shows a vertical cross-sectional view of a housing 100 for a planar circuit. Inside the housing 100, a circuit substrate 120 is mounted as shown in FIG. 1. The circuit substrate 120 is made of dielectric material such as epoxy, ceramics and the like. The top plan shape of the circuit substrate 120 is normally rectangular, but may be circular.
A planar circuit (not shown) is provided on a top surface, a bottom surface or both surfaces of the circuit substrate 120. The planar circuit provided on the circuit substrate 120 includes planar circuits such as filters which can be used for the microwave and millimeter-wave bands and other bands. The planar circuit is normally formed with conductor, but may be formed with thin films using superconductor.
The housing 100 is normally made of metal conductor such as copper. The housing 100 is a box-like body having spaces or cavities 180, 182 therein. An outer surface of the housing 100 can be covered with a gold plating. As shown in FIG. 1, internal walls or surfaces of the housing 100 are provided with two step portion 141. A lower portion of the housing 100 is a base portion 142. A lower surface of the base portion 142 can be contacted to a cooling stage (not shown) to cool the whole housing 100 including the substrate.
A lid 144 covers an upper portion of the housing 100. By removing the lid 144, the circuit substrate 120 can be mounted onto the two step portion 141. After mounting the circuit substrate 120, the lid 144 is mounted on the upper portion of the housing 100 to package.
As shown in FIG. 1, bonding wires 160 are provided for connecting between ground conductors 126 and the two step portion 141 of the housing 100. The bonding wires 160 can be formed of a good conductor such as a gold wire.
In this structure, the planar circuit can be electromagnetically shielded from the outside. An example of such housing is disclosed in Japanese Patent Publication 10-13105.
However, when obtaining the characteristics of such circuit substrate 120 contained in the planar circuit housing 100, there is a problem that it is difficult to prospect undesired waveguide transmission mode generation because that two cavities above and below the circuit substrate have different sizes in length and width.